An ammonium fluoride gas may be used to form a protection layer for one or more interlayer dielectric layers, one or more insulating caps, and/or one or more source/drain regions of a semiconductor device during a pre-clean etch process. The protection layer can be formed through an oversupply of nitrogen trifluoride during the pre-clean etch process. The oversupply of nitrogen trifluoride causes an increased formation of ammonium fluoride, which coats the interlayer dielectric layer(s), the insulating cap(s), and/or the source/drain region(s) with a thick protection layer. The protection layer protects the interlayer dielectric layer(s), the insulating cap(s), and/or the source/drain region(s) during the pre-clean process from being etched by fluorine ions formed during the pre-clean process.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method, comprising: providing a first amount of an ammonia gas and a second amount of a nitrogen fluoride gas into a processing chamber to cause an ammonium fluoride gas to form at a rate satisfying a threshold rate; forming, based on providing the first amount of the ammonia gas and the second amount of the nitrogen fluoride gas, the ammonium fluoride gas in the processing chamber at the rate to cause a chemical reaction between the ammonium fluoride gas and an oxide layer on an insulating cap, a dielectric layer, and a source or drain region of a semiconductor device in the processing chamber, wherein the chemical reaction causes a fluorosilicic layer to form on the insulating cap, the dielectric layer, and the source or drain region, and wherein the fluorosilicic layer has a thickness greater than 14 nm over the insulating cap and the dielectric layer; and removing the fluorosilicic layer from the source or drain region.
2. The method of claim 1 , wherein forming the ammonium fluoride gas comprises: causing, using a plasma source, a reaction between the ammonia gas and the nitrogen fluoride gas, wherein the reaction between the ammonia gas and the nitrogen fluoride gas causes formation of the ammonium fluoride gas.
3. The method of claim 2 , wherein a ratio between the nitrogen fluoride gas and the ammonia gas is greater than 1:5.
4. The method of claim 1 , wherein forming the ammonium fluoride gas comprises: forming the ammonium fluoride gas to cause the chemical reaction between the ammonium fluoride gas and the oxide layer as part of a pre-clean process.
5. The method of claim 1 , wherein the fluorosilicic layer is a protection layer that protects the source or drain region from being etched.
6. The method of claim 5 , wherein the protection layer reduces an amount of fluorine ion etching of the source or drain region.
7. The method of claim 1 , wherein removing the fluorosilicic layer comprises: heating the semiconductor device to cause the fluorosilicic layer to decompose into a plurality of gases; and removing the plurality of gases from the processing chamber.
8. The method of claim 7 , wherein heating the semiconductor device comprises: heating the semiconductor device to a temperature equal to or greater than 90 degrees Celsius.
9. The method of claim 1 , further comprising: forming a metal silicide layer for the source or drain region after removing the fluorosilicic layer.
10. The method of claim 9 , further comprising: forming a contact for the source or drain region, wherein the metal silicide layer reduces contact resistance between the source or drain region and the contact.
11. A method, comprising: providing, as part of a pre-clean process, a first amount of an ammonia gas and a second amount of a nitrogen fluoride gas into a processing chamber to cause an ammonium fluoride gas to form at a rate satisfying a threshold rate, wherein a ratio between the second amount of the nitrogen fluoride gas and the first amount of the ammonia gas is greater than 1:5; forming, as part of the pre-clean process and based on the ammonium fluoride gas being formed at the rate, a protection layer above an insulating cap, a dielectric layer, and a source or drain region of a semiconductor device, wherein the protection layer is formed of an ammonium fluoride salt from the ammonium fluoride gas, wherein the protection layer has a thickness greater than 14 nm above the insulating cap and the dielectric layer; wherein the protection layer protects the source or drain region from being etched by fluorine ions during the pre-clean process, and wherein the protection layer reacts with an oxide layer on the source or drain region to remove the oxide layer from the source or drain region; and removing the protection layer after performing the pre-clean process.
12. The method of claim 11 , wherein providing the first amount of the ammonia gas and the second amount of the nitrogen fluoride gas comprises: providing a flow of a gas mixture of the ammonia gas and a nitrogen trifluoride gas, wherein the nitrogen trifluoride gas comprises greater than 20% of the gas mixture.
13. The method of claim 11 , wherein a chemical reaction between the ammonium fluoride salt and the oxide layer causes formation of a fluorosilicic acid salt in at least a portion of the protection layer; and wherein removing the protection layer after performing the pre-clean process comprises: removing the fluorosilicic acid salt and the ammonium fluoride salt after performing the pre-clean process.
14. The method of claim 13 , wherein removing the fluorosilicic acid salt and the ammonium fluoride salt after performing the pre-clean process comprises: heating the semiconductor device to cause the fluorosilicic acid salt and the ammonium fluoride salt to decompose into a plurality of gases; and removing the plurality of gases from the processing chamber in which the semiconductor device is located.
15. The method of claim 14 , further comprising: forming, after removing the fluorosilicic acid salt and the ammonium fluoride salt, a contact for the source or drain region, wherein the contact is a self-aligned contact that is formed at least partially over a silicon nitride cap and a metal gate of the semiconductor device.
16. A method, comprising: providing a first amount of an ammonia gas and a second amount of a nitrogen trifluoride gas in a processing chamber to cause a reaction between the ammonia gas and the nitrogen trifluoride gas that forms an ammonium fluoride gas in the processing chamber, wherein providing the first amount of the ammonia gas and the second amount of the nitrogen trifluoride gas causes ammonium fluoride gas to form at a rate satisfying a threshold rate; forming, based on the ammonium fluoride gas being formed at the rate, a protection layer above an insulating cap, a dielectric layer, and a source or drain region of a semiconductor device to protect the source or drain region from being etched by fluorine ions resulting from the reaction between the ammonia gas and the nitrogen trifluoride gas, wherein the protection layer has a thickness greater than 14 nm above the insulating cap and the dielectric layer and a thickness of 4-5 nm above the source or drain region; cleaning, without use of isotropic plasma, an oxide layer from a surface of the source or drain region based on a reaction between the oxide layer and ammonium fluoride in the protection layer, wherein the reaction between the oxide layer and the ammonium fluoride in the protection layer causes at least a portion of the protection layer to transition to a fluorosilicic acid; and heating, after cleaning the oxide layer from the surface of the source or drain region, the semiconductor device to remove the protection layer from the source or drain region.
17. The method of claim 16 , wherein the source or drain region is an epitaxial region; and wherein the protection layer increases an epitaxial loss window of the epitaxial region.
18. The method of claim 16 , wherein heating the semiconductor device comprises: heating the semiconductor device to a temperature equal to or greater than 90 degrees Celsius.
19. The method of claim 16 , further comprising: forming a titanium silicide layer for the source or drain region after removing the protection layer; and forming a contact for the source or drain region, wherein the titanium silicide layer reduces contact resistance between the source or drain region and the contact.
20. The method of claim 1 , further comprising: performing a pre-clean process without use of isotropic plasma.
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September 1, 2020
June 28, 2022
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